Control system



Jan. 18, 1966 c. F. CZERNEK 3,229,588

CONTROL SYSTEM Filed Aug. 5, 1953 6 Sheets-Sheet 1 C. F. CZERNEK CONTROLSYSTEM Jan. 18, 1966 6 Sheets-Sheet 5 Filed Aug. 5, 1963 Wm N Jan. 18,1966 c. F. CZERNEK CONTROL SYSTEM 6 Sheets-Sheet 4 Filed Aug.

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CONTROL SYSTEM Filed Aug. 5, 1963 6 Sheets-Sheet (:qjefrzek UnitedStates Patent Ofilice 3,229,538 Patented .lan. 13, 1966 3,229,538CGNTRDL SYSTEM Clyde F. Czernelr, Sepulveda, Qalii, assigncr to WestonHydraulics, Limited, Van Nuys, Qalifi, a corporation of Cmifornia Filed5, 1963, Ser. No. 299369 7 Claims. ((11. 91387) This invention relatesto a control system for an actuator and more particularly to a servocontrol system.

Briefly described, the invention includes a novel hydraulic digitalconverter which in turn includes a plurality of cylinder-piston addersarranged in series. Each cylinder-piston adder is actuated independentthe adjacent cylindenpiston adders. The first adder in the series reactsagainst a fixed reference point and as a given piston extends orretracts Within its cylinder, the length of the series of adders changesa corresponding amount. The total movement of the adder assembly is thusdetermined by the combined cumulative displacements of the pistons withrespect to their respective cylinders. A novel combination ofcylinder-piston displacements plus a unique mode of actuating theindividual adders makes the hydraulic digital converter especiallysuitable for use in a servo system. The servo system may include afeedback linkage from the actuator to the hydraulic digital converter.

A more complete understanding of the invention will be readily aparentto those skilled in the art from the specification and appended drawingillustrating a certain preferred embodiment in which:

FIGURE 1 is a schematic representation of one embodiment of the servocontrol system;

FIGURE 2 is a view, partially in cross section, illustrating theactuator and its associated relationship with the servo system;

FIGURE 3 is a view, partially in cross section, taken generally alonglines 3-3 of FEGURE 2;

FIGURE 4 is a view, partially in cross section, taken generally alonglines 44 of FIGURE 2;

FIGURE 5 is a partial view, partially in cross section, of the digitalconverter component and the control valve component of the servo system;

FIGURE 6 is a view, partially in cross section, illustrating thehydraulic digital converter component of the servo system;

FIGURE 7 is a view, partially in cross section, taken generally alonglines 77 of FIGURE 6;

FIGURE 8 is a view, partially in cross section, taken generally alonglines 3-3 of FIGURE 6; and

FIGURE 9 is a schematic representation of an alternate embodiment of theservo control system.

Referring now to the drawing and more particularly FIGURE 1, theactuator housing 2%} is provided with opposed openings 22. and 24. Anactuator piston rod 25 extends through the openings 22 and 24. Thepiston rod 26 includes a first end 2-3 reciprocally received Within aground member 39 of the actuator housing. The ground member 3% isadapted to be pivotally connected to ground by way of pivot hole 32. Theactuator piston rod as carries an actuator piston 34 which is locatedwithin the chamber 3-6 of housing as. Ports 38 and 49 communicate withchamber 36 on opposite sides of the actuator piston A flow control valve42 is provided to direct fluid under pressure from a source of fluidunder pressure to chamber 36 and to direct fluid from chamber 36 to areturn line. The flow control valve 42 includes a bore 44, spool 45 andports 43, Si), 52, 54 and 56. The spool includes lands 58 and (all aswell as feedback end 62 which is connected to feedback link 64. An inletpassage 65 is connected to a source of fluid under pressure and isarranged to supply fluid under pressure to port 43 which port is locatedintermediate lands SS-ll in bore An outlet passage 6% is adapted tocommunicate ports 5d-52 with a fluid return line. Port St! is positionedin the bore 44 between land 58 and the left end of the bore 4 and port52 is positioned in the bore 44 between land 6% and the right end ofbore 44.

The digital converter '70 includes an elongated bore 72 having anopening 74 at one end thereof. A plurality of adders 76 is providedwithin the bore 72. Each of the adders 7s includes a cylinder 78slidably positioned within the bore 72. Each cylinder 78 is providedwith spaced apart lands 89 which provide sealing contact between theirrespective cylinders and the bore 72. Each of the cylinders is providedwith a chamber 82 and an opening 84 extending from the chamber 82 to theexterior of the cylinder 73. The cylinders include a port 86 which islocated intermediate the spaced apart lands 3%. The port providescommunication between the bore 72. and the chamber 82. An adder piston88 is provided within each chamber 82. Each of the adder pistonsincludes an adder piston rod 9% which extends through passage 8 into thebore '72.

The adders 76 are preferably arranged in series in a manner such thatenergization of an adder with the resultant movement of the individualpiston with respect to its associated cylinder (its stroke) results inthe elongation of the total series of adders by an amount equal to thestroke of the cylinder-piston adder. In other words, a movement of anindividual piston through its stroke (a predetermined distance) withrespect to its cylinder results in the same displacement of therespective ends of the cylinders of the total adder series.

A biasing means 92 is provided at one end of the bore 72. The biasingmeans includes a biasing cylinder 94 having spaced apart lands Q65: and%b on the exterior surface thereof which lands form a seal with the bore72. The biasing cylinder 94 includes an internal chamber 98 and anopening 10E extending into the bore '72. A piston 162 is reciprocablymounted within the internal chamber 98. The piston includes a piston rod104 extending through the opening 1th) into the bore F2. A port 106 isprovided through the wall of the biasing cylinder 94 between the spacedapart lands 96a and 9%. The primary function of the biasing means 92. isto collapse the series of adders (cause the pistons to retract withintheir cylinders) in the absence of fluid under pressure being suppliedto the individual adders. System pressure is fed to bore 72 by way ofport Hi5 and acts against land 31: to force biasing cylinder lid to theright. The force exerted by system pressure in an individual adder issufficient to overcome the force exerted by system pressure acting onland sea. A restrictor 97 is located in port 1%. The purpose of therestrictor is to control the reaction speed of the complete set ofadders. This is necessary to minimize the retrograde, or reversal instroke, which can occur due to differences in actuation time of theindividual adder. The biasing cylinder 94 includes an end portion 1%which extends through the opening 74. The end portion W8 is adapted tobe connected to the feedback link 64 by way of pin 110. The disclosedbiasing means is of the hydraulic type; however, it will be readilyapparent to those skilled in the art that other biasing means may besubstituted as a means of collapsing the adders. Likewise, theconnection between the digital conveter and the feedback link has beenillustrated as connected to the biasing means. Substantially similarresults may be achieved by connecting the feedback link directly to theadder series.

An important characteristic of the individual adder is the fact that ithas two operating positions; one of which is with the piston fullyretracted, and the other of which is with the piston fully extended.Another important characteristic of this arrangement of adders is thatthe stroke of the series of adders is equal to the sum of the stroke ofthe individual adders.

Individual independent input signal means 112 is provided to admit fluidfrom the pressure source to each of the adders. The input signal meansdisclosed in FIGURE 1 includes a plurality of solenoids 114 which admitfluid from the inlet passage 66 through valves 116 and passages 118 tothe bore 72 intermediate the lands 80 of the cylinders 73 of theindividual adder assemblies. These solenoids 114 further provide for therelease of fluid from the chambers 82 by Way of passages 118, and valves12% to exhaust pressure by way of outlet passages 68.

A polarity adder 122 includes a solenoid 124 and valve 126 with seats125 and 127. Valve 126 is adapted to assume two positions; the first ofwhich admits fluid from the supply source by Way of the passage 66 andpassage 128 to bore 72 intermediate lands 96 on the biasing cylinder 94and port 106 into the internal chamber 93 of the biasing cylinder 94,and the second of which admits fluid from the internal chamber 98, port106 and passage 123 into outlet passage 68.

A particularly important feature of the present invention is the strokeof each individual adder with respect to the stroke of the other adders.A preferred arrangement is with the stroke of the first adder in theseries of a predetermined length and each additional adder in the serieswith a stroke equal to two times the stroke of the preceding adder.These strokes can be set for any value compatible with the code beingused. The number of cylinder-piston adders used in the series determinesthe maximum number of positions which can be selected. With thepreferred relationship of relative strokes set forth hereinabove, themaximum number of control positions is governed by the formula:

Where P=number of positions and n=number of cylinder-piston adders. Atypical program utilizing the embodiment illustrated in FIGURE 1 isgiven in the following table:

Table I SERVO SYSTEM CODE Solenoid Nos. Position No. Actuator positionassess l-UJpPCJIG'i Maaaaaaaaaagaaaaaaaaaaaaaaaaaaaa NNPFPFFl-t-FZ. oOYh- 2CQ8 mcwootoo 4 Table IContinued SERVO SYSTEM CODE Solenoid Nos.Position No. Actuator position 0000:9'0 macaw-0:09

. www wsw s s w s s m ws i wi s i s s sw X denotes solenoid-adder asactuated.

FIGURE 9 illustrates an alternate embodiment of a control systemutilizing an actuator A, a four-way valve V, a digital converter DC, afeedback linkage F, input signal means S and a resilient biasing meansB. This embodiment utilizes a resilient biasing means to collapse theindividual adders upon de-energization of their respective solenoids.This biasing means is used in lieu of the hydraulic biasing meansdisclosed in FIGURE 1. This alternate embodiment also differs from theFIGURE 1 embodiment in that the feedback link is connected to the adderassembly.

Referring to FIGURE 1 and the operation of the system, fluid underpressure is supplied by way of inlet passage 66 to port 48, valve 116,valve 126, and port 105. Assuming valves 116 are closed and valve 126 isseated on seat 127, fluid under pressure from inlet passage 66 is fed tobore 72 by way of port and this fluid acts against land 96a to shift thebiasing cylinder 94 to the right, thus collapsing the individual adderassemblies. Energization of an individual solenoid 114 causes valve 116to open and valve 120 to close. This admits fluid from inlet passage 66to passage 118, and bore 72 intermediate lands 80. This fluid passesthrough port 86 into the adder chamber 82, thus causing the adder piston88 and the adder cylinder 78 to shift with respect to each other suchthat the adder piston rod 919 is fully extended. As each additionalsolenoid is energized, its respective valve members 116 and 120 operateas described hereinabove and its associated cylinder-piston adderassembly is activated to extend the adder piston rod 9%) from the end ofits cylinder an amount equal to the stroke of the cylinder-piston adder.As each adder is activated, the overall length of the series of addersis increased an amount equal to the stroke of the individual energizedadders. Any one, none, all of, or any combination of the adders may beactuated at a specific time.

As a means of controlling the actuation time of the individual adderassemblies, each solenoid output channel 118 is equipped with athrottling restrictor 117. As can readily be ascertained, the adderswith small displacements will complete their travel in a shorter periodof time than that required for the longer stroke adders if each weresubjected to the same pressure and flow conditions. The subjectrestrictors 117 are uniquely sized in such a Way that the resultingrestrictors impose limitations on the pressure and flow being suppliedby the solenoid valves 114 and 124 and hence equalize the actuation timeof each of the individual adder assemblies.

An increase in length of the series of adders results in movement of endportion 103 to the left. This causes feedback link 64 to shift to theleft thus changing the position of the four-way valve spool 46. Land 58moves from a position blocking flow through port 56 thus allowing fluidunder pressure in here 44 to pass through port 56, port 38 and intochamber 36 thus shifting the actuator piston 34 to the right. Land 69 ofspool 46 moves from a position blocking port 54 thus permitting flow offluid from chamber 36 through port 43 and bore 44 through port 52 intooutlet passage 68. As the actuator piston 34 moves to the right,feedback link 64 carries the feedback end 62 of the valve spool to theright thus repositioning lands 58 and 69 in a position blocking ports 56and 54, respectively.

The above procedure of operation is substantially reversed uponde-energization of the solenoid. For example, de-energization of thesolenoid causes valve 116 to close and valve 129 to open. This vents thefluid in chamber 82 through port 86, passage 118 and valve 120 to outletpassage 68. Fluid under pressure from inlet passage 66 is fed to bore'72 by way of port 105 and this fluid acts against land 96a of biasingcylinders 94 thus shifting the biasing cylinder to the right. Thebiasing cylinder causes the deflating adder to collapse. This shortensthe overall length of the adder series and shifts the end portion 198 ofthe digital converter to the right. Movement of the end portion 108causes the feedback link 64 to shift the feedback end 62 of the spool 46to the right. Land 60 is moved from a position blocking flow throughport 54 thus permitting fluid to flow from port 48 through port 54 andport 49 into the actuator chamber 36 thus shifting the actuator pistonto the left. At the same time, land 58 of spool 46 is moved from aposition blocking flow through port 56 thus permitting fluid to flowfrom chamber 36 through ports 38, 56 and 5-!) into outlet passage 68 toexhaust pressure.

Movement of the actuator piston to the left carries feedback link 64 tothe left re-positioning feedback end 62 of the valve spool 46 such thatlands 6% and 53 block the flow of fluid through ports 54 and 56respectively.

The polarity adder which consists of biasing cylinder 94, piston i432and its associated valve 126 provides for extreme simplification of thedigital program code for the servo system. The stroke of piston 102 withrespect to the biasing cylinder 94 is preferably at least equal to thecumulative stroke of all the other cylinder-piston adder units. With theprovision of the polarity adder, it is possible to tie-energize all thecylinder-piston adder solenoids as well as the polarity adder solenoidand obtain a null position of the piston actuator 34- at a substantiallycentral location within the actuator housing. Thus, with the polarityadder solenoid 124 (re-energized, it is possible to obtain 32 separatepositions of the piston actuator on one side of null and with thepolarity adder solenoid energized it is possible to obtain 32 separatepositions of the piston actuator on the other side of null. Thisparticular digital code program, utilizing the combination ofcylinder-piston actuators and solenoids as disclosed in FIGURE 1, ispreferable in that a loss of electrical power to the system results inpositioning the actuator piston at null rather than hard right or hardleft.

The servo system disclosed herein is capable of precise positioning andis suitable for use in aircraft and missile flight control surfaceactuation, missile nozzle gimbling actuation, machine tool controls, andother control systems wherein digital incremental control is desired.

Manifestly, the construction as shown and described is capable of someadditional modification and such modification as may be construed tofall within the scope and meaning of the appended claims is alsoconsidered to be within the spirit and intent of the invention.

I claim:

1. A servo system comprising an actuator housing, a fluid operatedactuator reciprocally mounted in said housing, a source of fluid underpressure, digital-analog means, conduit means providing communicationfrom said source of fluid under pressure to said ditigal-analog meansand from said digital-analog means to said actuator, said digital-analogmeans being responsive to an input signal eifective to communicate fluidfrom said source of fluid under pressure to said actuator to cause saidactuator to assume a predetermined position with respect to saidactuator housing, and feedback means connected to said actuator and tosaid digital-analog means effective to correlate the position of saidactuator with said input signal to said digital-analog means.

2. A servo system comprising an actuator having a housing and a pistonreciprocally mounted therein, a source of fluid under pressure, a flowcontrol valve in communication with said source of fluid under pressureand said actuator operative to admit fluid to said actuator andoperative to permit flow of fluid from said actuator, a digitalconverter connected to said flow control valve adapted to actuate saidflow control valve, conduit means providing fluid communication betweensaid source of fluid under pressure and said digital converter, inputsignal responsive means interposed between said source of fluid underpressure and said digital converter effective to provide actuation ofsaid digital converter by said fluid under pressure, and return conduitmeans communicating between said source of fluid under pressure and bothsaid digital converter and said flow control valve, and feedback meansconnected to said actuator and connected to said digital converterresponsive to correlate the position of said actuator with said digitalconverter.

3. A servo control system comprising a source of fluid under pressure, adigital converter responsive to fluid under pressure operative to assumea plurality of positions, input signal means connected to said source offluid under pressure and connected to said digital converter operativeto direct fluid under pressure from said source of fluid under pressureto said digital converter, an actuator responsive to fluid underpressure, flow control means connected to said digital converter andoperable thereby, first conduit means providing communication from saidsource of fluid under pressure to said flow control means, secondconduit means providing communication from said flow control means tosaid actuator and from said actuator to said flow control means, andreturn conduit means providing for return of fluid from said digitalconverter and from said flow control means to said source.

4. A servo control system comprising a source of fluid under pressure, adigital converter responsive to fluid under pressure operative to assumea plurality of positions, input signal means connected to said source offluid under pressure including conduit means providing communicationbetween said source of fluid under pressure and said digital converter,said signal means being operative to direct fluid under pressure fromsaid source of fluid under pressure to said digital converter foroperation thereof, an actuator responsive to fluid under pressure, flowcontrol means connected to said digital converter for operation thereby,conduit means providing communication between said source of fluid underpressure and said flow control means, between said flow control meansand said actuator, and return conduit means communicating between bothsaid digital converter and said flow control means and said source offluid under pressure, and feedback means interconnecting said actuatorwith said digital converter.

5. A servo control system comprising a source of fluid under pressure; adigital converter responsive to fluid under pressure operative to assumea plurality of positions; input signal means connected to said source offluid under pressure and connected to said digital converter operativeto direct fluid under pressure from said source of fluid under pressureto said digital converter; an 34 tuator responsive to fluid underpressure; flow control means connected to said digtal converter foractuation thereby, first conduit means communicating between said sourceof fluid under pressure and said flow control means, second conduitmeans communicating between said flow control means and said actuator,and return conduit means communicating between both said digitalconverter and said flow control means and said source of fluid underpressure; and feedback means interconnecting said actuator, said flowcontrol means, and said digital converter.

6. A servo control system comprising an actuator having a housing and afluid actuated reciprocating member positioned therein, a source offluid under pressure, a digital converter, conduit means communicatingbetween said source of fluid under pressure and said digital converter,means communicating between said source of fluid under pressure and saidactuator to provide flow of fluid to and from said actuator, saiddigital converter being responsive to a plurality of predeterminedcoding signals to admit fluid to said actuator through saidcommunicating means, and return conduit means communicating between saiddigital converter and said source of fluid under pressure to provide apredetermined displacement of said digital converter, and feedback meansconnected to said actuator and to said digital converter responsive tomaintain said actuator at a position corresponding to a particular codesignal.

7. A servo control system comprising an actuator having a housing and afluid actuated reciprocating member positioned therein, a sourc of fluidunder pressure, a flow control valve, conduit means communicatingbetween said source of fluid under pressure and said flow control valve,conduit means communicating between said flow control valve and saidactuator, a digital converter in fluid communication with said source offluid under pressure and connected to said flow control valve responsiveto a plurality of predetermined coding signals operative to cause apredetermined movement of said flow control valve to admit fluid to saidactuator, return conduit means communicating said flow control valve andsaid digital converter with said source of fluid under pressure andfeedback means connected to said actuator responsive to stop the flow offluid from said flow control valve to said actuator as a function of theparticular code signal fed 0 to said digital converter.

References Qited by the Examiner UNITED STATES PATENTS 2,931,375 4/1960Lewis 91384 2,969,042 1/1961 Litz 91167 2,974,639 3/1961 OConnor 913852,977,984 4/ 1961 Barnes 137625.64 3,000,363 9/1961 Hayner 137625.643,054,388 9/1962 Blanton 91-385 3,141,388 7/ 1964 Bran'stadter 9 l167SAMUEL LEVINE, Primary Examiner.

FRED E. ENGELTHALER, Examiner.

1. A SERVO SYSTEM COMPRISING AN ACTUATOR HOUSING, A FLUID OPERATED ACTUATOR RECIPROCALLY MOUNTED IN SAID HOUSING, A SOURCE OF FLUID UNDER PRESSURE, DIGITAL-ANALOG MEANS, CONDUIT MEANS PROVIDING COMMUNICATION FROM SAID SOURCE OF FLUID UNDER PRESSURE TO SAID DIGITAL-ANALOG MEANS AND FROM SAID DIGITAL-ANALOG MEANS TO SAID ACTUATOR, SAID DIGITAL-ANALOG MEANS BEING RESPONSIVE TO AN INPUT SIGNAL EFFECTIVE TO COMMUNICATE FLUID FROM SAID SOURCE OF FLUID UNDER PRESSURE TO SAID ACTUATOR TO CAUSE SAID ACTUATOR TO ASSUME A PREDETERMINED POSITION WITH RESPECT TO SAID ACTUATOR HOUSING, AND FEEDBACK MEANS CONNECTED TO SAID ACTUATOR AND TO SAID DIGITAL-ANALOG MEANS EFFECTIVE TO CORRELATE THE POSITION OF SAID ACTUATOR WITH SAID INPUT SIGNAL TO SAID DIGITAL-ANALOG MEANS. 